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Wolves on Michigan’s Isle Royale reveal new info about predator-prey relationships
This we know: Top carnivores profoundly influence local ecosystems.
By STARRE VARTAN October 26, 2018.
The American people’s relationship with top predators — especially wolves — is complex and ever-evolving. About three decades ago, it was mostly just animal-rights groups and their supporters who fought for the wolves’ right to exist; they were often considered a nuisance. But now there’s plenty of scientific evidence proving what’s good for wolves is good for their prey, the plants those prey eat, and indeed, positively affects the entire ecosystem. That’s ultimately good for humans too — unless you’re competing with the wolves, like a rancher who grazes animals or a hunter who wants to shoot the same deer or moose that wolves need to eat. But at this point, even some ranchers and hunters have come over to the pro-predator side.
Much of that change in the perception of predators is down to studies that have proven how precisely cougars, wolves, bears, tigers, lions, bald eagles, alligators and other apex predators affect the land around them. None have been studied longer than the wolves and moose in Isle Royale National Park, a Guam-sized island in Lake Superior. For almost 60 years, the populations of these two groups have been tracked — as well as their effects on the plants and other animal communities on the island. (You can read the reports here, including the recent 59th annual report.)
As the video above explains, there used to be as many as 50 wolves on Isle Royale; however, that number has dwindled, mostly due to inbreeding that caused a debilitating spinal condition to proliferate among the too-closely-related wolves. Just 10 years ago, there were still around 30 wolves but by 2015, there were only three wolves left. Now, there are just two, a closely related male-female pair that probably won’t breed. (The female of the pair has aggressively fought back when the male attempted to breed with her.)
Already, the moose population on the island has boomed, “undoubtably because of lack of predation,” John Vucetich, a wildlife ecologist from Michigan Technological University told Science magazine, adding that the two remaining wolves are now “… swimming in moose.” Despite the wolves’ regular predation on moose, there’s been a 20 percent increase in moose in just one year, which scientists estimate is about five to 10 times higher than on mainland areas. Beaver populations have also risen sharply. There’s just not enough wolves to keep either population in check.
So what’s so bad about so many moose? Well, as most ungulates do, moose spend their days browsing on vegetation, so the more moose, the more food they need — and the plants on the island can only take so much nibbling. An aquatic plant, which was found in abundance just six years ago, is now only found in places where moose are not. Long-term, this means the island will soon run out of food to keep the ever-larger moose population alive, and many will starve once food becomes scarce. Previously, the wolves have kept moose populations low enough so they didn’t overeat the vegetation, keeping the system in balance.
A plan to rebalance the ecosystem
This is why some people think the best solution is to bring a fresh influx of wolves to Isle Royale National Park. The plan is to release 25-30 wolves over the next three to five years. So far, park officials have trapped four wolves on the mainland beginning in late September and released them on the island. Three of the wolves are female — with the hope they will successfully breed.
This new blood would potentially rebalance the predator-prey relationship and the idea is that the rest of the ecosystem would follow. Introducing so many wolves over several years is hardly natural either, others argue, saying that humans should just be hands off and let nature take its course. The original 50 wolves had found their way to the island on their own, having moved in from Canada; perhaps they could do so again if given the chance.
Editor’s note: This article has been updated since it was originally published in April 2017.
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